COMPARISON OF BIOACCESSIBILITY USING PBET AND X-RAY ABSORPTION TECHNIQUES FOR RISK ASSESSMENT OF SELECTED LEAD CONTAINING MATERIALS

The assessment of lead ingestion by children requires accurate information on lead absorption (EPA, 2007). Bioavailability is the fraction of material in contact with a body portal-of-entry (lung, gut or skin) that enters the blood (IEUBK, 1999). In contrast bioaccessibility is the availability for absorption by the human body of target materials when dissolved in in vitro synthetic body fluids (Ruby et al., 1996) and absorbed by the gastrointestinal tract or lung prior to the blood stream (US EPA, 1994). The physiologically-based extraction test (PBET) gives a realistic assessment of lead bioaccessibility under fasting and fed condition for high dissolution of lead at low pH (Ruby et al., 1996; Basta and Gradwohl, 2000). Bioavailability varies widely among different lead forms in various environmental settings. Thus the relationship between speciation and bioavailability implies that a detailed identification is required of lead species in specific environmental media, such as air particulates, dust and solid waste (Brown et al., 1999) and other properties such as particle size. Synchrotron based X-ray absorption spectroscopy (XAS) is increasingly applied to determine lead speciation of solid phase samples (Manceau et al., 2002). In this study, a detailed comparison of lead speciation using XAS and bioaccessibility for selected lead containing materials is made. The comparison between bioaccessibility and lead forms provides a reasonable basis for source and hazard identification for risk assessment purposes.